Reckoning / Shape / Spandrel (fillet)
Plane figure · Circles
Spandrel (fillet)
The corner left between a right angle and a quarter circle that touches both sides, as in a rounded corner or a weld fillet.
Dimensions
Results
area A
Formulas
An r by r square minus a quarter of a disc of radius r.
Checked: the A formula agrees with a Monte Carlo measurement of the shape itself, made from its geometric definition, every time the site is built.
Topology lens
Topologically a disc, like every figure here without a hole: Euler characteristic 1. Stretching turns it into a circle, a square or a star. More on the lens.